We have previously shown that mouse eyes exposed to repeated periocular injection of the environmental toxicant hydroquinone (HQ) develop cytosolic actin aggregates at the retinal pigment epithelium (RPE) and incipient subRPE deposits. We hypothesize that HQ induces RPE mitochondrial dysfunction, which leads to development of this persistent injury phenotype. In this study, we sought to provide evidence that HQ injury in vivo was related to mitochondria dysfunction by measuring increased flavoprotein autofluorescnce (AF), an indicator of electron transport chain complex II dysfunction.

Methods

Two-month old C57BL/6J mice underwent bilateral periocular (subconjunctival) injections every three days with vehicle (PBS), 25 mM HQ, or 75 mM HQ (total five injections per group). At 14 days, animals were euthanized and saline-perfused. Eyes were harvested, and posterior eyecups were dissected with removal of the neurosensory retina. Freshly isolated RPE flatmounts were imaged by confocal microscopy with 488 nm excitation laser and barrier filter settings for oxidized flavoprotein AF. AF intensity was quantified for statistical analysis. In addition, flatmounts were stained with TRITC-phalloidin to evaluate aggregate formation. Preliminary studies correlated aggregate formation and mitochondrial function with pre-treatment with the mitochondrial targeted ubiquinone analog, idebenone.